Some experts say the tack of the judge who blocked parts of the Arizona law leaves her ruling vulnerable to reversal on appeal. But it may stand if the high court follows precedent on immigration.

The Supreme Court, where the legal controversy over Arizona's immigration law is likely to be resolved, has taken a dim view in recent years of judges striking down state laws based on broad challenges to laws that have not taken effect.

U.S. District Judge Susan Bolton agreed Wednesday with the Obama administration that much of the Arizona law was unconstitutional "on its face," without waiting for evidence that individuals were hurt or had their rights violated by state officials.

In her ruling, Bolton read the Arizona law broadly to apply to "all arrestees" in the state, not just those for whom there is a "reasonable suspicion" they are in the country illegally, as the state's lawyers interpreted the law. Relying on her understanding of the law's scope, Bolton said it was unconstitutional because legal immigrants and U.S. citizens "will necessarily be swept up" by it.

Some legal experts say the judge's approach leaves her ruling vulnerable to being reversed on appeal.

"She rejected the state's own interpretation of its statute, which is fundamental error in my view," said John Eastman, a law professor and former dean at Chapman University School of Law in California. "And she struck it down on a facial challenge, which is another significant error."

Yale law professor Peter Schuck agreed that the judge might have acted too soon. "By entertaining a facial challenge rather than waiting for an 'as applied' challenge, she jumped the gun," he said. Doing so left her without "the benefit of a real set of facts to use in assessing the statute's meaning and constitutionality," he said. "She also gave short shrift to the presumption of constitutionality that federal judges are supposed to bring to any challenge to state statutes."

However, Bolton's decision may stand if the Supreme Court follows its precedents on immigration, which have held that the responsibility for immigration law rests entirely with the federal government. Her opinion relied heavily on a 1941 ruling in which the justices struck down a Pennsylvania law that required aliens to carry an identification card. She quoted Justice Hugo Black's comment that such a state identification system would infringe on "the personal liberties of law-abiding aliens" and subject them to threat of "police surveillance."

Experts in immigration law generally gave Bolton high marks in following the court's past precedents. "It's a careful and well-reasoned opinion," said Hiroshi Motomura, a UCLA law professor. She followed the long-standing court precedent that said immigration enforcement is for the federal government, not the states, he said.

The judge focused on one sentence of the Arizona law that said, "Any person who is arrested shall have the person's immigration status determined before the person is released." Even though the state said it was targeting illegal immigrants, Bolton said its law as written would affect "the lives of legally present aliens and even United States citizens."

"That's a powerful and important aspect of this opinion. She recognized this is going to lead to harassment and interrogation of people who are here lawfully," said American Civil Liberties Union lawyer Omar Jadwat.

On Thursday, Arizona Gov. Jan Brewer asked the 9th Circuit Court of Appeals to lift the judge's order in early September and allow the law to take effect.

If the state loses before the liberal-leaning 9th Circuit, it is almost sure to appeal to the more conservative Supreme Court.

The outcome there may depend on whether the justices rely on their past precedents on immigration or follow their more recent skepticism toward broad challenges to state laws.

Led by Chief Justice John G. Roberts Jr., the court in the last five years has insisted on narrower, targeted suits that challenge how laws work in actual practice.

The Supreme Court will hear a different Arizona immigration case this fall. The state wants to dissolve any business that repeatedly and knowingly hires illegal immigrants. The U.S. Chamber of Commerce, joined by the Obama administration, say this state regulatory measure should be struck down because it conflicts with federal immigration law.

The outcome could shape the battle over the Arizona arrest law, said Temple University law professor Peter Spiro. "There's a good chance the court will use this lower profile case to make a broad pronouncement" on the state's authority to enforce immigration, he said.